Re: Short Plenum Run Question

[Frank Olson <Use_the_email_links@xxxxxxxxxxxxxxxxxxxxxx>]

robertlbass@xxxxxxxxxxx wrote:

> At first glance I didn't take exception to Mr. Olson's suggestion of
> using BX to jacket non-plenum rated cable.  That advice is incorrect.
> For fire safety reasons, NEC prohibits this practice if the run exceeds
> 4 feet and its use is restricted to cables required to operate the duct
> system itself.  It's not allowed as a means of avoiding using plenum
> cable.


I stated: "In Canada, damper motors are wired with mineral jacketed
cable or armoured BX.  There are also restrictions with respect to how
much cable can be exposed.  Check with your local building codes and
your AHJ to be on the safe side."  What part of my "advice" was
incorrect, Robert??  Perhaps it would be better if you didn't just
"glance" at my posts, but *read* them before you responded.


>
> NEC discusses the above as follows: "Flexible metal conduit and
> liquidtight flexible metal conduit shall be permitted, in lengths not
> to exceed 1.2 m (4 ft), to connect physically adjustable equipment and
> devices permitted to be in these ducts and plenum chambers."

And I stated:  "There are also restrictions with respect to how much
cable can be exposed.  Check with your local building codes and your AHJ
to be on the safe side."


>
> Also, if you do choose to use BX in those limited applications where it
> is permitted you must use connectors which "effectively close any
> openings in the connection."  IOW, you can't just slip a cut off piece
> of BX jacket over your regular cable and run it in a duct or plenum.


You're wrong there, buddy.  This part refers to the type of *connection*
allowed inside a duct and doesn't refer to runs *through* a duct.  From
what I understand you're not even allowed to make runs *through* a duct
at all, but only *to* equipment controlling devices that have to do with
the duct (fan blowers, dampers, shutters).  The sections of the NEC you
just posted confirms this.  And once again, I'd like you to point out
*where* my advice was incorrect.